The fatal crash took place on the A71 just west of the village of Wilkieston at around 7.10am on Thursday.
A 65-year-old woman pedestrian died following the collision involving a blue Ford Fiesta car travelling west at the time.
The 20-year-old male driver of the car was uninjured.
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The road was closed for around five hours to allow for an investigation.
Sergeant Peter Houston of the Road Policing Unit in Livingston said: “Our thoughts are with the family of the lady involved.
"Enquiries are still continuing to establish the full circumstances of what happened in this tragic incident.
“I am appealing for anyone who may be able to help us and in particular any drivers on the A71 at the time who may have dashcam footage showing either the lady or car involved.
“Anyone with information can call 101, quoting incident 0524 of 16 December.”